Copper-clad laminates for use in printed circuit boards were originally drilled to receive components mounted on the board. However, in an effort to reduce costs, drilling has been replaced by punching. In order to punch "clean" holes through the laminates, it is necessary to use special resin compositions in preparing the laminates. These compositions must be sufficiently flexible so that the punch does not fracture the board, yet they must also have the stiffness and other mechanical properties required to hold the components in position, as well as good electrical properties such as a low dielectric constant.
While some laminating compositions have overcome some of the problems encountered in punching laminates, such as a halo effect that occurs around the holes (see U.S. Pat. No. 4,477,512), these compositions have not solved the problem of cratering. Cratering occurs when the punch exits the opposite side of the board and a small amount of board breaks away from around the hole. With some components that are mounted on the board, cratering does not create any problems. However, when a component is mounted on the board in the form of a small tube that passes through the hole, cratering can prevent solder from flowing by capillary action into the tube. As a result, mass soldering by dipping the board into liquid solder cannot be used to mount these components, and the soldering must be done by hand, which is, of course, much more expensive.